Centrifugal switch



June 19, 1928.

, E. C. BALLMAN CENTRIFUGAL SWITCH Filed Oct. 8, 1924 Patented June 19, 1928.

PATENT, OFFICE.

EDWIN G. BALLMAN, OF ST. LOUIS, MISSOURI.

CENTRIFUGAL SWITCH.

Application filed October 8, 1924. Serial No. 742,295.

This invention relates to centrifugal switches, and more particularly to such switches as are used on electric motors for the purpose of changing the winding connections as the speed changes.

I One of the objects of this invention is to provide a centrifugal switch of novel construction provided with make and .break contacts which will protect the main contact surfacesfrom corrosion due to arcing.

Another object is to provide a switch of this type which will be simple and economical to manufacture and which will be rugged and durable in service.

Further objects will appear from the detail description taken in connection with the .accompanying'drawing, in which:

Figure 1 is .a face View of a switch embodying this invention as seen from the end of the motor shaft;

Figure 2 'is a similar view of part of the switch showing the contacts in contacting position; and

Figure '3- is a section on line 3-3, Figure 1. I

Referring to the accompanying drawing, 1 designates a frame or base upon which the various switch parts are mounted. This frame is provided with a central opening surrounded by an inturned flange 2 adapted to be fitted to the motor shaft 3 for mounting the switch thereon as shown in Figure 3. The frame 1 is provided with a peripheral rim or flange 4. Mounted on but insulated from the rim 4 is a, series of relatively fixed contacts 5 provided with binding screws 6 at which the necessary connections to the mo tor winding may be made.

In the embodiment illustrated, three pairs of contacts 5'are provided which are adapted to handle three motor circuits. Between each pairof contacts there is mounted a radially disposed rod 7. This rod is fitted into suitable perforations in the rim 4 and the flange 2 and is held in place by a locking plate or keeper 8 engaging a reduced shoulder 9 on the rod 7, the plate or keeper 8 being slotted to fit said shoulder. Mounted to slide onand'be'guided by the rod 7 is a main iarybridging contact 12 which fits snugly over the contact 10 but has its contacting tips 13 extending beyond the tips 11 of the main contact. The auxiliary contact 12 is entirely independent of the main contact 10, except that its movement is controlled by said latter contact. A spring 14 surrounds the rod 7 hearing at one end against the keeper 8 and serving to hold the same against dislodgment and at the other end against the main contact 10 so as tomaintain the same as well as the auxiliary contact 12 against the flange 2 and out of contacting position. I

The springs 14: are adjusted in tension so that when the motor attains a predetermined speed, the contacts 10 and with them the contacts 12 will move radially outward ly along and be guided by the guide rod 7 so as to bridge the contacts 5. The movement of the contact 10 is restrained by the spring 14 and the movement of the contact 12 is controlled by that of the contact 10. Since the ends 13 of the auxiliary contact extend beyond thoseof the main contact 10, these ends 13 will make contact with the contacts 5 before the ends 11 come into contact there with. 'As the speed of the motor falls off, the reverse of these operations will take place. The tension of the springs 14 will first overcome the centrifugal force of contact 10 and force the same away from the contacts 5. Afterward the contacts 10 will come into engagement with the, contacts 12 12 makes contact with the contacts 5 before and breaks contact after the engagement of, the main contact 10. Therefore, since the circuit is made and broken at the tips 13, these tipswill take all the pitting and corrosion incident to any arcing which may take place. Such corrosion would also occur on. the contacts 5'at a point spaced from that at which the tips 11 engage.

Since this switch is mounted on the motor shaft adjacent :the motor winding 15 the switch would-have a: tendency to shield the winding from ventilating air currents. In order toovercome this effect, the frame 1 is provided with ventilating openings which may have inturned flanges 16. These openings permit the passage of air through the frame 1 to the motor winding. On account of the fanning action of the winding itself there will ordinarily be established .a distinct suction effect tendingto pass the air through these openings and radially outward through the winding. The flanges 16 may assist in producing a fanning actionin order to additionally promote ventilation of the winding. 7

' It will be seen that in accordance with this invention. a switch is provided which may be mounted on the shaft of an electric motor for the purpose of controlling the circuits thereof, which has a simple structure adapted for making and breaking the contact on a set of auxiliary contact awhile the mainciicuit is maintained by a main bridgingcontact wh ch is protected agalnst corrosionby arcing, l he auxiliary contact makes the circuit first and breaks it after themain contact. The point of making and breaking is also spaced from the point of maintaining uniformly spacedaround the switch frame not only permit the circulation of air to the a winding but even assist n promoting a' circulation.

It IS obvious that var ous changes may t be, made in detailsof construction without departing'from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to thespecific details shown and described;

Having thus described the invention, what is claimed is:

j 1 A centrifugal switch for electric motors,

comprising, a supporting frame mounted on themotor shaft, relatively fixed contacts on said frame, a mam bridging contact having a. plurality of make and break. terminals centrifugally movable on frame and adapted to make and break contact with a plurality of, said fixed contacts, and an auxiliary bridgingcontact movable with said main contact and adapted to bridge said fixed contacts before said main contact,

2. A centrifugal switch for electric motors, comprising, a supporting frame mounted on the motor shaft, relatively fixed contacts onsaid frame, amain bridging contact having a plurality of make and break terminals centrifugally movable on said frame and adapted to make and break contract with a pluralityof said fixed contactsfand an auxiliary bridging contact movable wvith but regulated by said main contact and adapted to bridge said fixed contact-s before said main contact.

3. Acentrifugal switch for electric motors, comprising, a supporting frame mounted on the motor shaft, relatively fixed contacts on said frame, a main bridging contact having a plurality. of i nake and break termi-.

nals centrifugally movable on said frame and adapted to make and break contact with a plurality of said fixed contacts, and an auxiliary bridging contact movable with and i fitting said main contact and adapted. to

bridge said fixed contactsbefore said main contact.

4a A centrifugal switch for electric motors, comprising, a supporting frame mounted on the motor shaft, relativelyfixed contacts on said frame, a mainbridging contact having a plurality of make and break terminals centrifugally movable on said. frame and adapted to make and break contact with a plurality of said fixed contacts, and an auxiliary bridging contact movable with said main contact and adapted to contact independently with said fixed contacts, 5. A centrifugal switch for electric motors, comprising, a supporting frame mounted on the motor shaft,"relatively fixed contacts on said frame, a main bri'dging contact centrifugally movable on said frame and adapt-- ed to make and break contact with aplurality of said fixed contacts, and an auxiliary bridging contact movable with said main contact, and adapted to make independent centrifugal contact'with said fixed contacts.

6. A centrifugal switch for electric motors, comprising, a supporting frame mounted-on the motor shaft and having a rim, relatively fixed contacts on said rim, a radial guide on said frame, a main bridging contact centrifugally movable along said guide to bridge certain of said fixed contacts, and an auxiliary bridging contact centrifugally movable along f'said guide to contact with said certain fixed contacts.

17. A centrifugal switch for electric motors, comprising, a supporting frame mounted on the motor shaft and having a rim, relatively fixed contacts on said rim, a radial guide on said frame, a main bridging contact centrifugally movable along said guide to bridge certain of said fixed contacts, and an auxiliary bridging contact 'centrifngally movable along'said guide to contactwith said certain fixed contacts, said auxiliary contact extending beyond said main contact.

' 8. A centrifugal switch for electric motors, comprising, a. supporting frame mounted on the motor shaft and having a rim, relatively fixed contacts on said rim, a radial guid on said frame, a main bridging contact centrifugally movable along said guide to bridge certain of said fixed contacts, and an auxiliary bridging contact centrifugally movable along said guide to contact with said certain fixed contacts, before said main adapted to make and break contact with contacts. said pair of fixed contacts, one of said 9. Acentrifugal switch for electric motors, bridging contacts being adapted to bridge 10 comprising, a switch support mounted on the said fixed contacts in advance of the other. 5 motor shaft, a pair of relatively fixed con- In testimony whereof I aflix my signature tacts on said support, a plurality of centhis 14th day of August, 1924:. c trifuga-lly movable bridging contacts and EDWIN C. BALLMAN. 

